[en] Nowadays it is widely required that for the severe accident progression analysis and its associated phenomenology, be included the detailed study for behavior and diffusion of hydrogen inside of internal rooms and other areas in a Nuclear Power Plant, this is in order to avoid or minimize possible hazards and accidents because of hydrogen combustion . The analysis related to the behavior and reaction of hydrogen against changes over hardware or implementation of new features on systems, allows evaluate in an integral manner the possible risk through the simulation of scenarios by using the representative facility models, developed specifically for these cases. Thereby, the National Commission of Nuclear Safety and Safeguards - Mexico has been working since 2012 in the development of inputdeck models to analyze, for a wide spectrum of scenarios the behavior of hydrogen for several conditions, which allows establishing the criteria to evaluate the strategies of mitigation and control. (author)

[en] The paper aims to present an overview of the efforts and achievements reached in Mexico to develop a set of software for design and safety analysis for nuclear power reactors by AZTLAN platform project. This project aims to modernize, improve and incorporate the neutronics, thermo-hydraulics and thermomechanical codes developed as result of a joint work between institutions, universities and research institutes in Mexico, in an integrated platform, established and maintained for the benefit of the Mexican Nuclear knowledge. The scope of the software in their initial phase covers their use for training purposes in the regulatory authority as well as universities. (author)

[en] Three semi-empirical positron stationary Quantum Models were developed for the study of nanoporosity in a wide range of solid porous materials. The cubic, conic and cylindrical well potentials were considered and their geometric parameters related to the Positron Annihilation LifeTime (PALT) measurements. If a conic or a cubic symmetry is assumed, a resonance lifetime phenomenon was found, which enables proposal of a technique to catch positrons in free volume sites. In the cylindrical case, an alternative method to determine free volume sizes in materials was developed. The free volume equations of these new models were then compared to the well-known and widely utilised Spherical Free Volume Model (SFVM) and remarkable differences were found. A strong variation of the free volume size-positron lifetime relation with the geometry involved was observed and a remarkable dependence of the electron layer thickness parameter ΔR with the hole-shape under study and with the nature of the material considered. The mathematical functions appearing in the conic and cylindrical cases are the superposition of Bessel functions of the first kind and trigonometric functions in the cubic case. Generalised free volume diagrams were constructed and a brief geometrical scheme of the diverse cases considered was obtained. (author)

[en] Full text: Mexico presents its Tokamak Experimental Facility design under the necessary effort to develop Science and Technology into the thermonuclear magnetic confinement fusion area. This Research and Development Project (R and D) was approved from the Mexican Education Ministry (SEP, spanish acronyms) in 2007 for its development design stage at Facultad de Ingenieria Mecanica y Electrica (FIME) into the Universidad Autonoma de Nuevo Leon (UANL). We have made this effort in order to unify and consolidate under our tokamak experimental configuration facility (in the northern Monterrey city) the Mexican Energy Fusion Program and to participate in the nearest future, in ITER development, like the Mexican Fusion Research Group. The present design shows the development of a Tokamak Experimental Facility oriented to generate, innovate, understand, and develop scientific and technological knowledge, also to form researchers in the fusion confinement field Mexico desires with this initial effort to participate in the International Thermonuclear Experimental Reactor (ITER). This R and D Project involves multidisciplinary physics and engineering areas, that coexists into a nuclear fusion reactor, science and technology works together to establish a natural symbiosis between theory and experiments. We decide to use hydrogen plasma in this tokamak experimental facility with the next main characteristics: major radius 41 cm (R), minor radius 18.5 cm (a), aspect ratio 2.2162 (A), safety factor 1.9552 (q), plasma current 277 kA (I_p), β = 0.0532, toroidal field 1.3 T (B_t), ionic temperature 280 eV (T_i), electronic temperature 516 eV (T_e), electronic plasma density 2 - 3 x 10¹³ cm^-3(n_e). The stronger application of different sciences and technologies into our Mexican Energy Fusion Program, and the design and construction of this magnetic confinement device should allow us to develop, innovate and make significantly research exploding this new energy source concept, the magnetic confinement plasma is very complex, with this facility we can establish at first place our own schedule, a program to study and understand the different phenomena and with this aim, Mexico can participate in an integrate and intense collaboration with another nations in a great Research and Development International effort, like ITER does: A new energy source on earth. (author)

[en] External beam radiotherapy is the only practice in which humans are placed directly in a radiation beam with the intention to deliver a very high dose. This is why safety in radiotherapy is very critical, and is a matter of interest to both radiotherapy departments and regulatory bodies. Accidental exposures have occurred throughout the world, thus showing the need for systematic safety assessments, capable to identify preventive measures and to minimize consequences of accidental exposure. Risk-matrix is a systematic approach which combines the relevant event features to assess the overall risk of each particular event. Once an event sequence is identified, questions such as how frequent the event, how severe the potential consequences and how reliable the existing safety measures are answered in a risk-matrix table. The ultimate goal is to achieve that the overall risk for events with severe consequences should always be low o very low. In the present study, the risk-matrix method has been applied to an hypothetical radiotherapy department, which could be equivalent to an upper level hospital of the Ibero American region, in terms of safety checks and preventive measures. The application of the method has identified 76 event sequences and revealed that the hypothetical radiotherapy department is sufficiently protected (low risk) against them, including 23 event sequences with severe consequences. The method has revealed that the risk of these sequences could grow to high level if certain specific preventive measures were degraded with time. This study has identified these preventive measures, thus facilitating a rational allocation of resources in regular controls to detect any loss of reliability. The method has proven to have an important practical value and is affordable at hospital level. The elaborated risk-matrix can be easily adapted to local circumstances, in terms of existing controls and safety measures. This approach can help hospitals to identify vulnerable aspects and improvements required and regulatory bodies to improve the quality of their inspections. (author)

[en] Radiation safety has been based for many years on verification of compliance with regulatory requirements, codes of practice and international standards, which can be considered prescriptive methods. Accident analyses have been published, lessons have been learned and safety assessments have incorporated the need to check whether a facility is ready to avoid accidents similar to the reported ones. These approaches can be also called 'reactive methods'. They have in common the fundamental limitation of being restricted to reported experience, but do not take into account other potential events, which were never published or never happened, i.e. latent risks. Moreover, they focus on accident sequences with major consequences and low probability but may not pay enough attention to other sequences leading to lower, but still significant consequences with higher probability. More proactive approaches are, therefore, needed, to assess risk in radiation facilities. They aim at identifying all potential equipment faults and human error, which can lead to predefined unwanted consequences and are based on the general risk equation: Risk = Probability of occurrence of an accidental sequence * magnitude of the consequences. In this work, a review is given of the experience obtained by the countries of the Ibero American Forum of Nuclear and Radiation Safety Regulatory Organizations, by applying proactive methods to radiotherapy practice. In particular, probabilistic safety assessment (PSA) used for external beam treatments with linear electron accelerators and two studies, on cobalt 60 therapy and brachytherapy using the risk-matrix approach are presented. The work has identified event sequences, their likelihood of occurrence, the consequences, the efficiency of interlocks and control checks and the global importance in terms of overall risk, to facilitate decision making and implementation of preventive measures. A comparison is presented of advantages and limitations of each method, in terms of feasibility of application in practice and of resources required. Finally, ways are proposed to extend this experience to other countries of the Latin-American and other regions. This work has been funded by the Ibero American Forum of Nuclear and Radiation Safety of Regulatory Agencies (the FORO) and carried out under its technical programme. (author)

[en] This paper presents the results of the Probabilistic Safety Assessment (PSA) to the radiotherapy treatment process with an Electron Linear Accelerator (LINAC) for Medical Uses, which was conducted in the framework of the Extra budgetary Programme on Nuclear and Radiological Safety in Iberian-America. The PSA tools were used to evaluate occupational, public and medical exposures during treatment. The study focused on the radiological protection of patients. Equipment Failure Modes and Human Errors were evaluated for each system and treatment phase by FMEA. It was aimed at obtaining an exhaustive list of deviations with a reasonable probability of occurrence and which might produce significant adverse outcomes. Separate events trees were constructed for each initiating event group. Each event tree had a different structure since the initiating events were grouped according to mitigation requirements. Fault tree models were constructed for each top event. The fault trees were developed up to the level of components. In addition to hardware faults, the fault trees included human errors associated with the response to accidents, and human errors associated with the treatment. Each accident sequence was quantified. The combination of the initiating event and top events through one fault tree was the method used to analyse the accident sequences. After combining the appropriate models, a Boolean reduction was conducted by computer software to produce sequence cut sets. Several findings were analysed concerning the treatment process and the study proposed safety recommendations to avoid them. (author)